JPS63266835A - Vapor-phase reactor - Google Patents

Abstract

PURPOSE:To provide cleaning effect equivalent to or more than a wet cleaning and to improve the throughput of a whole steps of manufacturing a semiconductor by arranging an ultraviolet ray irradiator and an oxygen gas and ammonia gas supplying unit to a load locking chamber. CONSTITUTION:A plasma CVD or plasma etching apparatus has a reaction chamber 10 and a load locking chamber 20. O2 gas and ammonia gas supplying means 30 is arranged at a suitable position in the chamber 20. O2 and ammonia gas supply amounts are regulated by a valve 32. The means 30 is connected to an ammonia gas supply source and an O2 gas supply source. In order to convey a GaAs wafer 3 into the chamber 10, an ultraviolet ray irradiator 40 is disposed on the ceiling of the load locking chamber at the position where wafer carrier means 22 waits in a state for holding the wafer 3. The irradiator 40 is a light source for irradiating an ultraviolet ray having 253.7nm or shorter of wavelength. The light source may, for example, use a carbon arc lamp, a xenon lamp, a mercury lamp or an excimer laser, etc. The ultraviolet light source most preferably uses a low-pressure mercury lamp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas phase reactor. More specifically, the present invention relates to a gas phase reaction apparatus that operates a mechanism for cleaning the surface of a GaAs-based wafer while it is waiting to be carried into a reaction chamber.

[Prior Art] In order to improve the performance and reliability of conductor elements, cleaning treatment holds a major key.゛Since the surface of the i-conductor is very sensitive, By minimizing the η staining, the stability and IL+ characteristics of the device are significantly improved. Therefore, in order to prevent contaminants that adhere to the conductor surface during the wafer manufacturing process from remaining in the finished product, contaminants must be carefully removed before gas phase reaction processes such as diffusion, oxidation, CVD, and evaporation. No.

Surface contaminants are generally molecular and ionic.

Can be classified into atoms.

Molecular contaminants include wax, resin, photoresist, oil, organic solvent residue, and the like.

Fingerprint fat also falls into this category. Molecular contaminants are attached to the substrate surface by weak static electricity. Contamination with organic matter causes polarization and ionic drift due to proton movement, especially in the surface-sensitive MO8 structure.

Ionic contaminants are physically or chemically adsorbed, but chemically adsorbed ions are more difficult to remove than physically adsorbed ions. Chemical reactions must be used to remove this. Among ionic contaminants, alkali ions such as Na1 are particularly harmful, and BT treatment causes threshold voltage drift and formation of an inversion layer1.
Causes surface leakage current generation.

Atomic contaminants can include polymeric groups such as Au+Ag+Cu. These segregate into crystal defects and pn
It lowers the junction breakdown voltage and also affects the lifetime of minority carriers, surface conduction, and other device parameters. To remove these metals, they are ionized using a liquid that dissolves the metals to prevent them from depositing on the surface again.

[Problems to be Solved by the Invention] Conventionally, such semiconductor devices or wafers have been cleaned by a chemical method called wet cleaning, which involves using a cleaning liquid.

Water alone may be used as the cleaning solution, but to enhance the cleaning effect,
Chemicals (eg, alkalis, acids, surfactants, organic solvents, etc.) that do not adversely affect semiconductor devices or wafers can be used.

As a washing method, (1) immerse in a water tank; (2) apply ultrasonic vibration in the water tank; (3) 50 to 100 kg/
Spraying water at a high pressure of cm2; (4) letting water flow while rubbing with a nylon or mohair cloth; etc.

In the case of the cleaning method (3) above, if the distance between the nozzle and the wafer is large, static electricity may be generated due to friction between the high-pressure water and the air, which may destroy the MOS device.

Such a water washing device must also be equipped with a drying device for post-processing. As a drying method, for example, a method is used in which the wafer is dried at high speed at several thousand rpm while blowing nitrogen gas. However, in this case, the blown water hits the wall of the device and bounces back.
There is a risk that it will re-adhere to the wafer and contaminate the wafer surface.

Dry cleaning methods include (1) cleaning by heating and flame treatment t%; (2) sputter cleaning t41; (3) cleaning by ion milling; C4) plasma cleaning.

In the case of flame treatment, there is a risk that the device may be deformed or destroyed due to thermal stress, so it can only be applied to metal substrates and the like. Sputtering, ion milling and plasma cleaning require high frequency power.

Therefore, in the conventional technology, in order to clean the surface of the wafer, a cleaning/drying process and equipment for the same must be specially provided in addition to the original gas phase reaction process and gas phase reaction apparatus.

5. If such a cleaning/drying step is placed before the original gas phase reaction step, the throughput of the entire semiconductor manufacturing process will be reduced. Moreover, a large amount of money and space is required to provide special washing and drying equipment, which increases the cost of the product.

Further, after cleaning and drying, the wafer may be oxidized or recontaminated by moisture, oxygen, etc. in the air while waiting to enter the gas phase reaction process.

In particular, the surface of Ga-As (gallium-arsenide) wafers, which have recently been attracting attention as wafers for manufacturing VLSIs, is oxidized and an oxide film is formed even if they are exposed to air after cleaning. If the oxide film is loaded into the reaction chamber and the original film forming process is performed with this oxide film left, the adhesion between the produced film and the wafer may deteriorate or cracks may occur in the produced film.

If annealing treatment is performed in a state where cracks still exist, As may be blown away. Furthermore, if the oxide film is heated to about 800° C. with the oxide film remaining, the resulting film will easily peel off from the wafer.

[Object of the Invention] Therefore, the object of the present invention is to eliminate special processes and equipment such as the conventional wet cleaning method and dry cleaning method.
It is an object of the present invention to provide a gas phase reaction device equipped with a dry cleaning device that does not require cleaning, has a cleaning effect equal to or better than wet cleaning, and does not reduce the throughput of the entire semiconductor manufacturing process.

[Means for Solving the Problems] As a means for solving the above-mentioned problems and also achieving the object of the present invention, the present invention provides a method for loading a GaAs-based wafer into at least a reaction chamber of a gas phase reactor. A gas-phase reaction apparatus in which a load-lock chamber is connected to a reaction chamber for performing a gas-phase reaction, characterized in that the load-lock chamber is provided with an ultraviolet irradiation device and an oxygen gas and ammonia gas supply device. A reactor is provided.

[Function] The gas phase reaction device of the present invention combines the effect of ultraviolet rays on the chemical bonds of organic compounds with the strong oxidizing effect of ozone, thereby converting organic stains into volatile substances (such as carbon dioxide).
02 + N2 + water, etc.).

Ultraviolet light with a wavelength of 240 nm or less absorbs oxygen and generates ozone 03 through the following reaction.

o + 02 -1 → 03 Also, 240n
Ultraviolet rays with wavelengths longer than 111 are not absorbed by 02, but are absorbed by ozone 03 to generate ozone again.

0 + 02 03 Wavelength 3 (The energy of 35 nm ultraviolet rays is approximately 78°3K)
cal/mol, but the wavelength is 253.7 nm and 1
The energies of 84.9 nm ultraviolet light are approximately 113 and 1, respectively.
It is 55 kcal/r6ol. On the other hand, the chemical bond energies of C-C and C-H are 83.1 and 98°8, respectively.
kcal/mol. That is, 365nI11
Although C-C and C-H bonds cannot be dissociated with light of 253.7 nm or less, they can be dissociated with light of 253.7 nm or less.

Therefore, according to the dry cleaning means of the present invention, contaminant molecules are ionized by ultraviolet light having a wavelength of 253.7 nrrl or less.

free radicals, dissociated into excited or neutral molecules,
When these come into contact with ozone, they produce C021N2 or N2
It is thought that it is decomposed into volatile molecules such as 0.

Most of the organic contaminants and air oxide films on the wafer surface can be removed by the above-mentioned treatment, but in the case of GaAs wafers, ultraviolet rays and ozone can oxidize the wafer surface to a depth of about 50 to 100 cm. Sometimes. This UV103 oxide film is P-8rN similar to the air oxide film.
As the degree of integration of semiconductor devices increases, they become undesirable because they reduce adhesion when capping and may cause cracks.

As a result of extensive experiments and research carried out by the present inventors over many years, we found that after the UV103 cleaning process was completed, ammonia gas was introduced into the load rotor chamber and ultraviolet rays were irradiated, as shown in the reaction equation below. Hydrogen ions are generated and G
It has been discovered that the oxide film on the surface of an aAs wafer can be reduced and removed.

[Embodiments] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a gas phase reactor having a dry cleaning means of the present invention, FIG. 2 is a perspective view showing an example of another gas phase reactor, and FIG. 3 is a lid portion thereof. It is a bottom view.

As shown in FIG. 1, a gas phase reactor (e.g., plasma CVD or plasma etching apparatus) 1 has a reaction chamber 10 and a sealable load lock chamber 20 for loading wafers into the reaction chamber.

Inside the reaction chamber 10, for example, a sample stage 12 on which the wafer 3 is placed and a plasma electrode 14 facing the sample stage 12 are arranged. In addition, there is an exhaust duct 1 at the bottom of the reaction chamber.
6 is provided. Needless to say, the internal configuration of the reaction chamber differs depending on each gas phase reactor.

The reaction chamber 10 and the load lock chamber 20 are separated by a gate 18 that can be opened and closed. Inside the load lock chamber 20, a wafer carrier means 22 that can move forward and backward for carrying the wafer 3 into the reaction chamber is provided.

02 gas and ammonia gas supply means 30 are arranged at appropriate locations in the load rotor chamber 20. 02 and ammonia gas supply amount can be adjusted with a valve 32. The supply means 30 includes an ammonia gas supply source (not shown) and an ammonia gas supply source (not shown).
2 connected to a gas supply source.

Further, an exhaust duct 24 is provided in the load lock chamber 20. This is done to evacuate the air in the load rotor chamber and create a high oxygen atmosphere, or to replace the gas and create an inert atmosphere. Ozone production efficiency can be increased by irradiating ultraviolet rays in a pure oxygen atmosphere than by irradiating oxygen in the air with ultraviolet rays.

An ultraviolet irradiation device 40 is disposed on the ceiling of the load lock chamber at a position where the wafer carrier means 22 waits while holding the wafer in order to carry the wafer 3 into the reaction chamber 10 . The ultraviolet irradiation device 40 can be installed not only on the ceiling but also on the floor. This is effective when the back side of the wafer also needs to be cleaned.

The ultraviolet ray irradiation device 40 is, for example, a light source that irradiates ultraviolet rays with a wavelength of 253.701 or less. As the ultraviolet light source, for example, a carbon arc lamp, a xenon lamp, a mercury lamp, or an excimer laser can be used. A mercury lamp is preferred from the viewpoint of ease of handling.

As the ultraviolet light source with a wavelength of 253.7 nm or less, a low-pressure mercury lamp is most preferable.

The shape of the mercury lamp is not an essential requirement of the present invention. Oval, 9-spherical, ring-shaped or U-shaped cane tubes can be used. A ring-shaped or U-tube type light source is preferable because it has a wide effective irradiation area, can uniformly irradiate the wafer, and can clean the wafer efficiently and uniformly.

When a fused quartz tube is used as a tube material for a low-pressure mercury lamp, it transmits light of 184.9 nm in addition to light of 253.7 nm. In high silica glass, 184.9 nm light is absorbed by the tube material and does not pass through to the outside.

Therefore, it is preferable to use a low pressure mercury lamp with a fused silica tube.

The number of mercury lamps is not an essential requirement of the present invention. At least one tree or more should be provided. The output of the lamp is likewise not a requirement of the invention. These are matters that can be easily determined by those skilled in the art, taking into consideration the dimensions of the load lock chamber, the size of the wafer, and the like.

To maximize cleaning speed, it is preferable to locate the ultraviolet light source as close to the wafer as possible. Although not particularly limited, as a general indicator, the divisor l1l
It is preferable to arrange the light source and the wafer at a distance within a range of about I11 to several CI+.

Instead of the example of the device in which the ultraviolet light source is installed on the ceiling of the load lock chamber as shown in FIG.
As shown in the figure, an apparatus may be implemented in which a ring-shaped low-pressure mercury lamp 42 is disposed on the lower surface of the lid member 62 for loading the wafer into the load-lock chamber 20 on the loader side and closing the opening 74 thereof. The shape of the mercury lamp may be a U-shaped tube or a sphere.

A ring or U-tube mercury lamp is preferred, in which the viewing window 66 of the lid is not covered.

The outline of the gas phase reactor shown in FIG. 2 will be explained. Details of this device are described in Japanese Patent Application No. 61-055748.

In the apparatus shown in FIG. 2, the load-lock chamber 20 on the loader side and the load-lock chamber 50 on the unloader side are arranged in an L-shape so as to be substantially orthogonal to the reaction chamber 10.

Each loader chamber has a gate valve (not shown)
It is separated from the reaction chamber by

A wafer supplied from a wafer cartridge (not shown) is placed on a hopper table 54 of a first wafer transport mechanism 52, and is advanced by a belt drive or an air bearer to reach a wafer track 56. First wafer detector 5
8 detects a wafer, the first wafer transfer arm 60 vacuum-chucks the wafer from below, rotates in that state, and the wafer holder disposed at the bottom of the first lid part 62 transfers the wafer to the transfer claw 6.
4, and place the wafer on the claw 2.

The first lid portion 62 has a viewing window 66 . The first lid portion 62 is screwed or fixed to an arm 72 that can be raised and lowered of the first lid opening/closing mechanism 70 . When the wafer is placed on the transfer claw 64 of the wafer receiver, the liftable arm 72 is lowered and enters the load lock chamber through the first opening 74 opened in the upper part of the load lock chamber 20 on the loader side. A wafer is placed on the wafer carrier means 22. The liftable arm 72 further descends,
The first lid part 62 covers the first opening part 74 and seals the load rotor chamber 20. The movement of the human body in the load rotor chamber on the unloader side is the opposite.

A wafer sample stage 12 is arranged inside the reaction chamber.

A wafer support claw 76 is provided around the wafer sample stand for holding a wafer placed on the sample stand. The claws of the wafer holder are configured to be replaceable according to the diameter of the wafer being used. Although not shown, the second part of the reaction chamber is covered with a top cover equipped with a reaction gas feeding nozzle and/or parallel plate electrodes, and the reaction chamber is hermetically sealed.

Next, the specific operation of wafer cleaning will be explained.

First, the wafer is loaded into the load lock chamber on the loader side, and the load lock chamber is sealed. Exhaust any air remaining in the room. When a predetermined vacuum pressure is reached, oxygen gas is fed into the room from the oxygen gas supply means. When the oxygen gas concentration in the room reaches a predetermined value, ultraviolet light is irradiated from the ultraviolet light source to perform wafer cleaning without generating ozone.

After cleaning is completed, residual oxygen gas and ozone in the room are exhausted, and ammonia gas is introduced in their place. When the concentration of ammonia gas reaches a predetermined value, ultraviolet rays are irradiated to generate hydrogen ions to reduce and remove the UV10a oxide film present on the surface of the GaAs wafer.

After the removal of the oxide film is completed, the ammonia gas or the like remaining in the chamber is replaced with an inert gas (for example, N2 or Ar). Thereafter, the cleaned GaAs wafer is carried into the reaction chamber.

It is preferable to maintain the oxygen gas concentration in the room between 20% and 100%. The cleaning time depends on the type of light source used and the distance between the light source and the wafer, but is generally within several tens of seconds to several minutes.

The following test was conducted to confirm the cleaning effect.

A finger was pressed onto the surface of a clean GaAs wafer to deposit sebum. This wafer was placed in a load lock chamber on the loader side of a gas phase reactor as shown in FIG. 2, and held by wafer carrier means. The lid was sealed and the distance between the UV light source and the wafer was set at 5+nm. After the oxygen gas concentration in the room was set to 100%, ultraviolet rays were irradiated. Judgment of cleanliness is
This was done by blowing steam onto the wafer surface and measuring the time until rainbow-like interference fringes appeared, which were uniform when the steam condensed and non-uniform when it evaporated.

For comparison, measurements were also made for cleaning with ultraviolet rays with a wavelength of 253.7 nm and ozone, cleaning with ultraviolet rays alone, and cleaning with ozone alone. The results are summarized in Table 1 below.

As is clear from these results, extremely short wavelength light (18
It is understood that the wafer can be cleaned within an extremely short period of time by combining the ozone generation caused by the reaction of 4,9n■) with oxygen and the chemical bond dissociation effect of short wavelength light (253,7nm).

When the surface of the GaAs wafer under cleaning condition (1) was analyzed, an oxide film having a thickness of about 100 to about 200 mm had been formed. This was returned to the load lock chamber, and ammonia gas was introduced, and when the gas concentration reached 100%, it became 184.9
Ultraviolet light with wavelengths of 253.7 nm and 253.7 nm was irradiated. The irradiation time was approximately 60 seconds. After the irradiation was completed, the surface of the wafer was analyzed again. As a result, it was confirmed that the thickness of the oxide film was reduced by half.

According to the dry cleaning means of the present invention, the sebum of the handler, adsorbed substances and oxides when left in the air, thin films of vacuum-deposited carbon, and other substances that may adhere to wafers or semiconductor devices, etc. °Tuning oil, vacuum pump and diffusion pump oil.

acidic solder flux, solder rosin flux,
Particularly suitable for removing stains such as silicone vacuum grease, polishing fluids, beeswax and rosin mixtures, etc.

Although the dry cleaning means of the present invention provides a sufficient cleaning effect by itself, conventional wet cleaning can also be used in combination as a pre-cleaning. By performing wet pre-cleaning, it is possible to remove in advance dirt such as dust and salts that do not become volatile products due to the oxidative decomposition effects of ultraviolet rays and ozone.Furthermore, crosslinking occurs due to the action of ultraviolet rays, resulting in UV-resistant A thick film that becomes a coating can be removed in advance.

As a result, it becomes possible to further enhance the dry cleaning effect of the present invention.

The ultraviolet and ozone dry cleaning means of the present invention can be used with a variety of gas phase reactors. For example, it can be used in semiconductor manufacturing equipment such as normal pressure, reduced pressure, plasma and photo CVD thin film forming equipment, dry etching equipment, epitaxial growth equipment, PVD metal film deposition equipment, oxidation/diffusion equipment, and the like.

In addition, it can also be used for all devices in which a load lock chamber is connected to a reaction chamber.

[Effects of the Invention] As explained above, the gas phase reaction apparatus of the present invention having a dry cleaning means using ultraviolet rays and ozone performs the cleaning process during the waiting time for carrying the wafer into the reaction chamber, so that the entire manufacturing process can be simplified. Throughput can be improved.

The oxide film generated when a GaAs-based wafer is cleaned by UV10J can be removed by being reduced by hydrogen ions generated by irradiating ammonia gas with ultraviolet rays. Therefore, the occurrence of inconvenient situations such as a decrease in adhesion and the occurrence of cracks due to the presence of the oxide film is effectively prevented or suppressed.

Since the dry cleaning means of the present invention comprises an ultraviolet light source and a large oxygen gas/ammonia gas delivery nozzle, the device configuration is extremely simple compared to conventional wet cleaning equipment, and requires very little installation space.

Furthermore, it has high cleaning efficiency for a wide range of organic stains, and can be operated at room temperature and pressure, making it extremely easy to handle and inexpensive to operate. Furthermore, the cleaning time is extremely short.
A highly cleaned surface can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a gas phase reactor having a dry cleaning means of the present invention, FIG. 2 is a perspective view showing an example of another gas phase reactor, and FIG. 3 is a lid portion thereof. It is a bottom view. 1... Gas phase reaction device, 3... Wafer, 10... Reaction chamber. 12... Sample stand, 14... Electrode, 16... Exhaust duct. 18...Gate, 20...Loader side load rotor chamber.

Claims (6)

[Claims] (1) In a gas phase reactor in which at least a load lock chamber for loading a GaAs wafer into the reaction chamber of the gas phase reactor is connected to the reaction chamber, the load lock chamber includes an ultraviolet irradiation device and an oxygen gas and ammonia irradiation device. 1. A gas phase reaction device, characterized in that it is equipped with a gas supply device. (2) The gas phase reaction device according to claim 1, wherein the ultraviolet irradiation device comprises a light source that irradiates ultraviolet rays with a wavelength of 240 nm or less and/or ultraviolet rays with a wavelength of 253.7 nm or less. (3) The gas phase reactor according to claim 2, wherein the ultraviolet light source is a carbon arc lamp, a xenon lamp, a mercury lamp, or an excimer laser. (4) The gas phase reaction device according to claim 3, wherein the mercury lamp is a low-pressure mercury lamp. (5) The gas phase reaction apparatus according to any one of claims 1 to 4, wherein an ultraviolet irradiation device is disposed near the wafer loading standby position in the load lock chamber on the loader side. (6) The gas phase reaction apparatus according to any one of claims 1 to 5, which is a plasma CVD or plasma etching apparatus.